Loading...
26 results
Search Results
Now showing 1 - 10 of 26
- Changes in plasma amino acid levels in a euryhaline fish exposed to different environmental salinitiesPublication . Aragão, C.; Costas, B.; Vargas-Chacoff, L.; Ruiz-Jarabo, I.; Dinis, Maria Teresa; Mancera, J. M.; Conceição, L. E. C.Previous studies have shown that Senegalese sole is partially euryhaline in the juvenile phase, being able to adapt to a wide range of salinities in a short-time period, due to changes at the osmoregulatory and metabolic level. This study aimed to assess the effects of acclimation of sole to a wide range of salinities, with a special emphasis on the role of plasma amino acids during this process. Sole juveniles were acclimated for 2 weeks to different salinities: 5, 15, 25, 38, and 55 g L−1. Plasma levels of cortisol, glucose, osmolality, and free amino acids were assessed at the end. Changes in plasma levels of cortisol, glucose, and amino acids indicate that fish reared at 5 and 55 g L−1 were facing extra energy costs. Amino acids seem to play an important role during salinity acclimation, either as energy sources or as important osmolytes for cell volume regulation.
- Improving weaning strategies for Senegalese sole: effects of body weight and digestive capacityPublication . Engrola, S.; Conceição, L. E. C.; Dias, L.; Pereira, R.; Ribeiro, Laura; Dinis, Maria TeresaTo optimize Senegalese sole-weaning strategies, three experiments were performed.The first trial tested four weaning strategies with a10mg sole. Artemia-fed sole grew threefold less than fish fed an inert diet. Sudden weaning (abrupt change from Artemia to inert diet) and weaning with co-feeding produced larger sole than did a late weaning treatment; delayed weaning negatively affected ¢sh growth. In the second experiment, the digestive capacity of early-weaned 1, 2 and 4mg sole was investigated. The highest growth was observed in sole weaned at 4mg. Digestive enzyme pro¢les suggest that sole have an adaptation period to inert diets, with reduced feed intake. This adaptation period is inversely proportional to post-larvae weight. The third experiment examined weaning with cofeeding at di¡erent weights (2,5 and11mg).These studies demonstrate that sole of 5^10mg can be weaned, with high survival rates. On the basis of the digestive enzyme pro¢les, the early introductionof inert diets in co-feeding with Artemia seems to affect intestinal processes in smaller postlarvae. This study also suggests that trypsin and alkaline phosphatase may be used as indicators of nutritional status in sole ofo5mg.
- Different environmental temperatures affect amino acid metabolism in the eurytherm teleost Senegalese sole (Solea senegalensis Kaup, 1858) as indicated by changes in plasma metabolitesPublication . Costas, B.; Aragão, C.; Ruiz-Jarabo, I.; Vargas-Chacoff, L.; Arjona, F. J.; Mancera, J. M.; Dinis, Maria Teresa; Conceição, L. E. C.Senegalese sole (Solea senegalensis) is a eurytherm teleost that under natural conditions can be exposed to annual water temperature fluctuations between 12 and 26C. This study assessed the effects of temperature on sole metabolic status, in particular in what concerns plasma free amino acid changes during thermal acclimation.
- High stocking density induces crowding stress and affects amino acid metabolism in Senegalese sole Solea senegalensis (Kaup 1858) juvenilesPublication . Costas, B.; Aragão, C.; Mancera, J. M.; Dinis, Maria Teresa; Conceição, L. E. C.; Refojos, B. C.Fish held at high stocking densities are generally exposed to chronic stress situations that impose severe energy demands and may predispose the ¢sh to infection. Senegalese sole Solea senegalensis (Kaup) juveniles (78.8 18.9 g body weight) were maintained at low (LSD; 4 kg m2 at the end of the experiment), medium (MSD; 9 kg m2 ) and high (HSD;14 kg m2 ) stocking densities during a period of 63 days. Although disease outbreaks were observed in ¢sh reared at HSD, growth and food consumption did not vary among di¡erent treatments. Results from plasma cortisol and free amino acids (FAAs) showed signi¢- cant di¡erences among di¡erent rearing densities pointing to HSD as stressful rearing condition.
- Free amino acids are absorbed faster and assimilated more efficiently than protein in postlarval Senegal sole (Solea senegalensis)Publication . Rønnestad, I.; Conceição, L. E. C.; Aragão, C.; Dinis, Maria TeresaTo improve the formulation of diets for the early stages of marine fish, assimilation rates of free amino acids (FAA) and protein in postlarval Senegal sole (Solea senegalensis) were determined. Fish (2.45 ± 0.87 mg dry weight) were tube fed 36 nL of a diet of FAA containing L-[35S] methionine (FAA diet) or bovine serum albumin, containing L-[methylated-14C]bovine serum albumin (Prot-diet), both at a concentration of 4.08 g/L. A time series was performed, and the amounts of label in incubation water, liver, gut and body carcass were quantified. The FAA diet was absorbed with a 3.5-times-higher transfer rate (P < 0.001) from the gut into the larval body tissues compared with the Prot-diet. The FAA diet also was assimilated with greater efficiency than the Prot-diet (80% versus 58%, P = 0.001). If we assume that the label present in the gut represents amino acids incorporated into the intestinal tissue, the assimilation efficiencies for the two diets were 89 and 64%. Therefore, FAA seems to be superior to protein as a dietary source of amino acids in Senegal sole postlarvae. However, because the absorption dynamics of protein and FAA differ, care should be taken when using the sources together to avoid amino acid imbalance.
- Co-feeding of inert diet from mouth opening does not impair protein utilization by Senegalese sole (Solea senegalensis) larvaePublication . Engrola, S.; Mai, M.; Dinis, Maria Teresa; Conceição, L. E. C.In most marine species inert diets alone have a poor ability to sustain fish larvae growth and development. Furthermore, results of co-feeding inert diets and live prey are variable, which may be related to the effect of inert diets on digestive maturation and subsequently protein utilization. The aim of the present work was to investigate how different feeding regimes, live feed alone or co-fed with an inert diet, influence protein utilization in Senegalese sole larvae. Feed intake, protein absorption, protein retention and protein catabolism were estimated in sole from 8 to 35 days after hatching (DAH), using 14C-labelled Artemia protein and posterior incubation in metabolic chambers. Postlarvae that were co-fed with an inert diet from mouth opening ate more than postlarvae fed Artemia alone at most sampling ages. Sole Artemia protein digestibility ranged from 56.97 (16 DAH) to 81.32% (22 DAH). Sole larvae that were fed a second meal had a slightly, though significant, higher digestibility than sole fed a single meal. Digestibility was lower in co-fed sole during metamorphosis climax, and similar between treatments at other developmental stages. Retention efficiency remained almost constant during early development, and was not affected by feeding regime. In short, co-feeding of an inert diet from mouth opening does not impair protein utilization by Senegalese sole larvae.
- Skeletal evaluation and technical improvements to decrease the incidence of skeletal deformities in Solea senegalensis, KaupPublication . Gavaia, Paulo J.; Richard, Nadège; Dâmaso, L.; Dinis, Maria Teresa; Pousão-Ferreira, P.; Engrola, S.; Conceição, L. E. C.; Cancela, LeonorThe appearance of skeletal deformities is a major problem associated to intensive, large-scale culture of fish species, affecting growth, development and ultimately, survival of produced fish. Although the mechanisms working behind it are still unclear, it is known that environmental, genetic and nutritional factors play fundamental roles. Given its importance as a vertebrate model to study skeleton-related diseases, the selection of an appropriate dietary protocol is a critical step in order to diminish the nutritional effect on bone and cartilage development. To better understand the effect of diet on skeletal development and deformities, as well as on larvae and juvenile global performance, we have tested four distinct dietary regimes, composed of rotifers Brachionus sp., Artemia nauplii and dry, formulated food.
- Stress response and changes in amino acid requirements in Senegalese sole (Solea senegalensis Kaup 1858)Publication . Aragão, C.; Corte-Real, Joana; Costas, B.; Dinis, Maria Teresa; Conceição, L. E. C.Fish in aquaculture are often exposed to various stressors that may change their ability to survive or limit growth. Amino acids are used for processes other than growth, including stress response. This study intended to analyse how repeated acute handling stress can affect growth and amino acid requirements in fish. Senegalese sole juveniles were weekly held in the air during 3min (Handling) for 9 weeks; Control groups were left undisturbed. Growth and plasma levels of stress indicators and of free amino acids were assessed at the end of the experiment. Plasma cortisol and osmolality levels showed that fish in the Handling treatment were stressed, but growth was unaffected. Plasma amino acid concentrations indicate that their requirements in stressed fish were altered, which probably reflects the synthesis of proteins or other specific compounds related to stress response.
- Hormonal induction of Atlantic dusky grouper (Epinephelus marginatus) broodstockPublication . Conceição, L. E. C.; Cabrita, Elsa; Engrola, S.; Lacuisse, M.; Pousão-Ferreira, P.; Dinis, Maria TeresaImmature fish and young females were sex reversed using hormonal induction in two consecutive years. In the first year one permanent male was obtained. Collected sperm of both years ranges from 30 μl to 300 μl and cell concentration varies from 3 to 6.5 x109 spermatozoa/ml. Atlantic dusky grouper can successfully be induced to functional males with 17α-methyltestosterone implants.
- Amino acid pools of rotifers and Artemia under different conditions: Nutritional implications for fish larvaePublication . Aragão, C.; Conceição, L. E. C.; Dinis, Maria Teresa; Fyhn, H. -J.The rearing of most marine fish species still relies on live food. Amino acids (AA) are the building blocks for protein synthesis, are important energy substrates, and are involved in specific physiological functions. Thus, the AA pools (free and protein-bound) of the rotifer Brachionus rotundiformis and of Artemia parthenogenetica metanauplii were analysed, after enrichment with different diets or at different salinities. The changes in these pools were related to their impact when used as feed for the developing fish larvae. Rotifers and Artemia were enriched for 24 h in microalgae, in commercial diets, or starved for the same time period. The enrichment at different salinities was also tested using Artemia. The free AA (FAA) quantity and quality was strongly affected by the enrichment used, in both rotifers and Artemia metanauplii. The relative FAA content was significantly higher in rotifers and Artemia enriched with microalgae than in the ones enriched with commercial products, and between the different microalgae tested, the enrichment in T. chui resulted in the highest FAA content for both preys. Differences regarding the FAA quantity and quality were also found between rotifers and Artemia. With the exception of the starved preys, a higher relative FAA content was found in rotifers than in Artemia metanauplii and while the FAA pool of the rotifers was dominated by alanine, taurine was the dominant AA in the FAA pool of Artemia. Salinity had only a small effect on the FAA pool of Artemia. Concerning the protein fraction, starvation increased the relative protein content in the rotifers. Among the metanauplii, the relative protein content was affected neither by the enrichment nor by salinity, except for a significantly lower content found when the microalgae Nannochloropsis gaditana was used. The quality of the protein pool is affected by the different enrichments, but not by salinity. However, the changes in the protein-bound AA pool were less pronounced than for the FAA pool and reflect differences in the protein content and/or quality of the diet. This study showed that the AA composition of cultured zooplankton is affected by feeding regime and by salinity. The choice of the best zooplankton enrichment and/or mixture of enrichments for the different fish larval stages, should take into account the AA composition, in order to fulfil the energetic and nutritional requirements of the larvae.
- «
- 1 (current)
- 2
- 3
- »